This invention relates to a process for producing a multi-layer web consisting of an exterior covering laminated with an adhesive layer on a nonwoven material which has a higher standing (i.e. perpendicular to the surface of the material) fiber portion.
Covering materials for upholstered furniture and particularly for vehicle seats, as well as softly backed covering parts, such as interior door coverings, should have a certain inherent stiffness. An inherent stiffness makes the material easier to handle when the coverings are sewn as well as when they are used, which is why covering materials are generally laminated on flexible-foam layers with thin polyurethane (PUR) foam webs. Covering materials prepared in this way not only feel softer than covering materials resting directly on the underpadding of the seat but such covering materials also retain a wrinkle-free form even after extensive usage.
It should be remembered in this context that, particularly in vehicles, persons may remain in essentially the same sitting position for several hours without interruption. Covering materials reinforced in this fashion do not become hung up on the back side, but slide well. Generally, the back side of the stiffened covering materials must also be provided with an air-permeable light textile web material, which are laminated onto the back side of the foam backing.
It is therefore understandable that such covering materials are quite expensive, particularly since the actual upholstery material alone is not inexpensive. Therefore, for the purpose of saving money, the above-mentioned layers of foam material, which have a thickness of approximately 2 to 8 mm, are generally used as the soft material layer as it is less expensive than nonwoven materials, although nonwoven materials provide for more comfortable seating.
The prerequisite for using a particular nonwoven material as backing for the upholstered material, is that the material must have sufficient permanent elasticity. Under the extended effects of heat, pressure and humidity, it must not be possible to permanently flatten the material but, at least after a certain cooling and drying time, the material must spring back to its original shape.
Generally, different webs, which in this case includes not only woven materials or knitted fabrics, but also nonwoven materials, such as leather or plastic, are joined with adhesives. Thus, for example, a woven web and a nonwoven material can be joined by placing the woven web on one side and the nonwoven material on the other side of a flat-bed laminating machine between pairs of guide bands which extend in parallel, straight lines which are closed on both sides, with heatable and coolable parts. According to this technique, the covering materials backed by foamed material can also be laminated.
However, flame laminating process are preferably used, in which approximately 0.6 mm of the PUR foam-material foil is melted off and the liquid melted PUR foam-material is used as the adhesive. Generally, different types of adhesives and adhesive application methods for webs, as well as drying and hardening processes are used. For example, one method involves the application of a film of melted adhesive consisting of fine individual points on one surface and joining same with the web. Another method involves placing a thin nonwoven material consisting only of binding fibers on one web side or letting such a binding fiber nonwoven material run between the webs to be glued together.
Different types of nonwoven materials which are suitable in this context, their applicability as car upholstery materials and testing methods are described for example in G. Schmidt, "Laminating Car Upholstery Materials by Means of Nonwoven Fiber Materials", Melliand Textilberichte 6/1992, pages 479 to 486, and "Spaced Knitted Fabrics with and without a Design Side for Applications in the Automobile", Melliand Textilberichte 1/1993, Series 1 and 2, pages 37 to 39, and pages 129 to 134, the disclosures of which are herein incorporated by reference. German Patent Document DE 91 16 536 U1 also discloses a multi-layer, textile covering material of this type, the disclosure of which is herein incorporated by reference.
Accordingly, multi-layer covering materials useful as car upholstery, in which a top material is laminated together with a nonwoven material which is in the form of a nonwoven knitted fabric is generally known in the art. Since the rear side of these covering materials has a type of knitted layer, a third rear-side protective lamination is not required here. The disadvantage of these covering materials, which with respect to seating comfort are superior to the foam-backed multi-layer alternative, is the manufacturing price, which is comparatively high despite being only two layers.
For this reason, this type of covering material has not been widely accepted as a substitute for the foam alternative despite its functional advantages. The higher cost results not only from the high-expenditure, multi-step manufacturing process of the nonwoven materials, specifically the manufacturing of plastics, fibers, and other nonwoven materials, as well as the bonding of the nonwoven materials by means of knotting, but also from the required calibrating operation. only a calibrated and smoothed, admixture-bonded nonwoven material offers the required prerequisites for a visually qualitative condition which is equal to the foam-backed covering materials.
U.S. Pat. No. 3,619,322, the disclosure of which is herein incorporated by reference, discloses a process wherein a nonwoven fiber material formed from a fiber mixture including so-called binding fibers is bound between two guide bands extending parallel and in a straight line by means of pressure and heat in such a manner that individual fibers can no longer be easily separated out of the exposed surfaces of the formed nonwoven material and that these nonwoven surfaces have a smooth and flat design. Binding fibers are fibers made of a thermoplastic material with a lower melting point than the remaining fibers of the nonwoven material. At least one of the guide bands is constructed as a sieve so that the heat in the form of hot air can be blown into the nonwoven fiber material or can be blown through it. In addition, by means of this bonding process, known as thermofusion, the nonwoven material has a predetermined uniform thickness, less adhesive on its surface and slightly more resistance to bending and shearing so that it can be more easily handled when processed into textile products.
Recently, a different type of binding fiber has been disclosed, specifically a so-called bi-component binding fiber in which two thermoplastic materials of different melting points, for example, 140.degree. C. and 220.degree. C., are processed in a concentric arrangement with the lower melting plastic on the outside to form a single fiber.
Based on the above-described methods, it is an object of the present invention to disclose a low-cost process for producing multi-layer webs having a highly uniform thickness, in which, because of the lower cost of the process, higher quality textile materials are available for use as the backing material of multi-layer textile or non-textile coverings or interior fitting materials and/or reprocessed fibers can be used, therefore increasing the potential for savings.
According to the present invention, this and other objects are achieved by a process for the continuous manufacture of a multi-layer web consisting of an exterior covering with a nonwoven material disposed underneath, wherein
the nonwoven material contains a portion of bi-component binding fibers and, of the fibers of the nonwoven material, at least 20%, preferably approximately 70%, of the fibers or of the fiber length portions are arranged approximately at a right angle with respect to the nonwoven surface, PA1 in the process, the nonwoven material, which has not been additionally bonded or calibrated, and the web of the exterior covering are jointly guided in a continuous manner between two guide bands extending in an approximately parallel plane and in a straight-line fashion, PA1 in which case increasing pressure is exercised on the two webs and heat is supplied by way of the closed and heated guide bands, PA1 as a result of which, in a uniform working step, PA1 the nonwoven material contains a portion of bi-component binding fibers and, of the fibers of the nonwoven material, at least 20%, preferably approximately 70%, of the fibers or of the fiber length portions are arranged approximately at a right angle with respect to the nonwoven surface, PA1 in the process, an additionally bonded, smoothed and calibrated nonwoven material is formed directly from pile or a loose nonwoven material, wherein for the additional bonding, smoothing and calibrating of the nonwoven material, the nonwoven material is continuously guided between two guide bands extending at a distance in an approximately parallel plane and in a straight-line manner, pressure being increasingly exercised on the nonwoven material and heat being supplied by way of the closed and heated guide bands, PA1 as a result of which, in a directly successive process sequence, PA1 subsequently, the additionally bonded and calibrated nonwoven material is laminated onto the web of the exterior covering while an adhesive is disposed in-between the layers.
the nonwoven material is additionally bonded by means of the bi-component binding fibers which melt on the outside and are embedded in the nonwoven material, and compressed by the pressure which is simultaneously applied in a laminar manner such that the thickness of the nonwoven material is reduced, PA2 the nonwoven material is calibrated and the exposed nonwoven surface is smoothed by means of the compression between the parallel guide bands under the effect of pressure and heat, PA2 and furthermore, the two webs are laminated upon one another by using an adhesive applied in-between. PA2 a voluminous, prebonded nonwoven material is formed, PA2 the nonwoven material is additionally bonded by means of the bi-component binding fibers which melt on the outside and are embedded in the nonwoven material, and is compressed by the pressure which is simultaneously applied in a laminar manner such that the thickness of the nonwoven material is reduced, PA2 the nonwoven material is calibrated and the exposed nonwoven surface is smoothed by means of the compression between the parallel guide bands under the effect of pressure and heat,
According to the present invention, this and other objects are also achieved by another process for the continuous manufacture of a multi-layer web consisting of an exterior covering with a nonwoven material disposed underneath, wherein
This invention relates to a cost-neutral substitution of the previously used foam material layers, which do not provide optimal sitting conditions, by textile webs having the same function which have a high standing fiber portion, which in the past had been more expensive but provide better sitting conditions than foam material layers. Several types of textile webs listed below have a high standing fiber portion and are usually nonwoven knitted fabrics of different makes. As a result of the combination of different manufacturing steps into a single process step according to the present invention, a cost advantage is achieved in the manufacturing of the multi-layer composite which from a cost standpoint, makes it competitive with foam-backed covering materials.
Additionally, the covering material provides better sitting conditions and is approximately equivalent to the foam-backed covering materials with respect to other physical textile comparative values. In particular, the covering material produced according to the present invention can be recycled in a much simpler and better fashion and without any functional disadvantages, recycled textiles can be used as reprocessed fibers into this covering material in a low-cost manner.
The two processes of the present invention cited above, differ in the cost-reducing combinations of steps. The first cited process starts out with a once prebonded nonwoven material, as defined below, as a separately produced initial product, wherein the steps of additional bonding, calibrating and smoothing of the nonwoven material as well as the lamination of the nonwoven material and the covering material are combined.
In contrast, according to the second process cited above, at least the steps of manufacturing a voluminous nonwoven material as well as the additional bonding, calibrating and smoothing of the nonwoven material are combined in the process. This can take place, for example, by directly joining the machines which form the nonwoven material with the process of thermofusing, calibrating and smoothing. This initial product of high quality manufacturing must then only be laminated together with the covering material. Here, it is also possible that this lamination step is combined in a sequence which is uniform with respect to the machine construction and the process, which has further cost-reducing effects.
In the sense of the present invention, the term "covering" is the textile or non-textile top side of upholstered or covering composites, particularly as used in the interior fitting of vehicles of all types and in living areas. This covering is either a textile material, such as a woven fabric, a knitted loop-type fabric or the like or a non-textile, flat material, such as leather, imitation leather, foil, a coated textile, or similar material. For the purpose of the present invention, this covering can be used as a web, a roll or as a surface-limited part, for example, as a prepared animal skin or as a cut textile blank for a seat.
The term "nonwoven material", refers to a flat fiber or filament arrangement in which the fibers or filaments are bonded, as opposed to being loose, by mechanical processes (for example, by nonwoven knitting or needles), by chemical processes (for example, by fiber-wetting adhesives) and/or by thermal processes (for example, by the start-melting of bi-component fibers) to form a cohesive flat-shaped structure. This bonding of the nonwoven fibers or filaments is required in order to facilitate handling. In the context of the present invention, this bonding should be understood only as a prebonding or initial bonding. In effect, according to the present invention, the nonwoven material is additionally bonded beyond this initial bonding as a result of the embedding and activating of bi-component binding fibers into the nonwoven material. This results in higher physical textile pressure and elasticity values similar to those of a foam material. In the case of a normal nonwoven material, such additional bonding would be unacceptable because of cost limitations. However, in the present invention, this additional bonding step is harmonically and cost-effectively combined with the laminating step which is necessary anyway.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention.